assume cs:code
code segment
    mov ax, 4c00h
    int 21h 
    start:	mov ax, 0
    s:	nop
    	nop

    	mov di, offset s
    	mov si, offset s2
    	mov ax, cs:[si]
    	mov cs:[di], ax

    s0:	jmp short s

    s1:	mov ax, 0
    	int 21h
    	mov ax, 0

    s2:	jmp short s1
    	nop
code ends

end start

